Many of Sterling Research's patients have participated in these cholesterol trials.

Small clinical trial is just one of 12 to run until 2018 * Sanofi, Regeneron hope to seek drug approval by late 2015

NEW YORK/PARIS (Reuters) - A new type of cholesterol drug from Regeneron Pharmaceuticals Inc and Sanofi SA, when used by itself, cut levels of "bad" LDL cholesterol almost in half in the first of a dozen late-stage trials of the medicine.

The injectable drug, called alirocumab, is from a promising new class of medicines called PCSK9 inhibitors also being developed by Amgen Inc and other drugmakers. It has been touted by industry analysts as a potential blockbuster that could bring annual sales of over $3 billion.

These man-made antibodies block a protein that prevents the body from eliminating LDL cholesterol from the bloodstream and offer a new way of fighting the build-up of artery-clogging fatty deposits that put patients at risk of heart attacks.

They work differently from widely-used statins - pills that inhibit the liver's production of LDL cholesterol in the first place, and to which some patients don't respond well.

In earlier mid-stage studies, when combined with statins, alirocumab and Amgen's own PCSK9 drug cut levels of LDL cholesterol by close to 70 percent, more than statins alone.

But the Phase III study unveiled on Wednesday involved patients who either took just alirocumab, or just Merck & Co Inc's cholesterol drug Zetia (ezetimibe) - a pill often used by patients who cannot tolerate statins, whose side effects can include muscle pain.

In this 103-patient study, alirocumab, which has to be self-injected every two weeks, reduced levels of LDL cholesterol by 47.2 percent after 24 weeks of treatment, compared to 15.6 percent in those taking daily 10-milligram doses of ezetimibe.

"What we're seeing in the first Phase III trial of our drug is in line with what we saw in Phase II," George Yancopoulos, Regeneron's research chief, said in an interview.

"The good news here is there were no surprises, and that it supports the good efficacy and safety profile we've seen to date."

Patients taking alirocumab started out with a low 75-milligram dose every two weeks, but this was increased to 150 milligrams at week 12 if their LDL levels at week eight were above 70. Most patients, however, remained on the low dose throughout the study because they got their LDL levels below that threshold - an aggressive LDL target - by the eighth week.

"It shows that a low dose, when used as a monotherapy, can be quite effective," Yancopoulos said, noting that no worrisome side effects were seen in the study nor in earlier trials.

Shares in Sanofi, which rose 0.8 percent in early trade, were down 0.8 percent at 1150 GMT, roughly in line with the STOXX Europe 600 Healthcare index.

Citi analyst Andrew Baum said the monotherapy data was "incrementally positive" but further trials on targeted patient groups, such as patients with high cardiovascular risk, were needed to really assess the drug's utility.

Patients in the so-called Odyssey Mono trial had high cholesterol levels but were deemed to have only moderate cardiovascular risk due to the absence of many other risk factors.

FIVE MORE YEARS OF TRIALS

The Odyssey Mono study is the first of 12 Phase III trials on some 23,000 patients and the drug's ultimate success will depend on longer-term studies, some of which will only give results in around five years. But Sanofi and Regeneron are hoping positive trial data could be enough to get the drug approved for some patients and on the market before then.

PCSK9 drugs are mainly aimed at the millions of people who either cannot tolerate statins such as Pfizer Inc's Lipitor or AstraZeneca Plc's Crestor or who cannot get their cholesterol levels under control with statins alone.

Yancopoulos said Regeneron and Sanofi hope to seek regulatory approvals by late 2015 for their drug, for use by itself and with statins.

Yancopoulos said Amgen's rival drug might reach market soon after alirocumab, or even before. But he predicted neither drug would have much of an advantage by getting approved first.

"But we're hoping to have bragging rights for the first approval," Yancopoulos said.

At an investor conference last month, Sanofi's CEO Chris Viehbacher said the drugmaker could look at nearly doubling its stake in Regeneron, voicing confidence in the drug's success. Sanofi holds about 16 percent of Regeneron.

Deutsche Bank analysts said in a report last month that the new drug could be priced at around $15 per day, comparable to the cost of injectable diabetes drugs known as GLP-1s, such as Novo Nordisk's Victoza.

"Today's results should go some way to building confidence in Sanofi's improving pipeline capability and in our view forms the first step to bridging credibility following recent poor financial results," Deutsche Bank wrote in a note on Wednesday.